1. Field of the Invention
The present invention relates to a leakage detecting device for electrical appliance. More particularly, the present invention relates to a leakage detecting device adapted to prevent a leakage accident such as injury to a human body by an electric shock and a damage to an electrical appliance such as a hair dryer or a hair iron when it has fallen into water or other liquid.
2. Description of the Prior Art
In a house of the latest design, a dressing table is often installed within a bath room. In such a case, if an electrical appliance such as a hair dryer or a hair iron with the power plug thereof being put into theplug receptacle has been dropped, by mistake, into the water of a bath tub or the like, there is a fear that an accident such as injury to a human body by an electric shock may occur. As the prior art for detecting leakage to prevent such an accident due to an electric shock, a technique as disclosed in British Patent Specification No. 1,408,316 or the Japenese Patent Publication Gazette No. 7885/1985 is known. A leakage detecting device indicated in the Japanese Patent Publication Gazette No. 7885/1985 uses a zero-phase current transformer so that when a ground current flows from a load to the ground, a difference between the input and output currents flowing in the zero-phase current transformer is detected as an induced voltage for the zero-phase current transformer to cause the contact to be turned off.
However, if an electrical appliance (a load) has been dropped in the water of a container such as a bath tub having a high insulation property, a leakage current flows in the water, and if a human in the water receives an electric shock, it is difficult for a zero-phase current transformer to detect the leakage current because a current equal to the leakage current returns to the power source, and the water and the power source also function as a part of the load. Furthermore, since a zero-phase current transformer detects generation of a minor leakage current, it is necessary to make it have a high sensitivity, which involves disadvantages in that the signal-to-noise ratio is not good and the zero-phase current transformer is liable to be affected by a magnetic noise from the exterior, causing erroneous operation. In addition, such a conventional device has a large number of components and is large-sized, and accordingly, the manufacturing cost thereof becomes high.